Research And Improvement On The Reliability Of The Backlight Source For Liquid Crystal Display

Back Light is a key optical component of LCD.Quality of the back Light display directly determine quality of the LCD.As the LCD and backlight becomes thinner and thinner,two reliability problems arises which include foreign body&white point and luminescent inequality.This thesis is to find the foundamental of these two problems,to establish evaluation method,and to resolve the two problems.The main results of the thesis are as shown as followed.(1)Formation of reliability white point&foreign matter is film layer is caused by pressing of the membrane layer and the film layer of the particle.Then it is important to reduce the number of foreign bodies in the process,to improve the pressure resistance of the membrane material and the concealer of the film material,and to develop non-soft particle diffusion films.Through the establishment of vacuum adsorption,environmental testing methods(high temperature and humidity,cold and heat shock),defect probability of the LCD backlight source decreased from-15%to 1%,which was significantly improved.(2)The waving caused by the expansion of membrane material is another major problem decreasing yield of the back light.The waving is mainly caused by the large expansion coefficient of the membrane material,the small gap between the membrane material,the rubber frame,and the inconsistent expansion coefficient of the membrane material and the adhesive glue..Therefore,a matching model of membrane material and adhesive layer was established.Low shrinkage rate material and process optimization were developed to ensure the assembly gap.As varified by high temperature expansion coefficient test and environment test(high temperature,high humidity,hot and cold shock,cyclic temperature and humidity changes),the defect probability caused by uneven lighting of the back light was found to reduced from 9%to 2%.(3)This paper also finds that even with a moderate gap between the assembling clearance and suitable material expansion coefficient,the membrane material can still be wrinkled.This problem was ascribed to the film material itself.The research results above provide a complete solution for the backlight source material and dimension design.